1. Field of The Invention
The present invention relates generally to a cam arrangement, particularly to a cam arrangement which can be employed in a loading/unloading mechanism of an apparatus utilizing cassettes, such as a VTR, for example.
2. Description of The Prior Art
The functioning of a conventional cam arrangement for a Video Tape Recorder (VTR) will be explained with reference to FIG. 7. As seen in the drawing, a fixed portion 101 is engaged with a slidably installed portion, or sliding chassis, 102. A fixed cam member 103 and a movable cam member 104 are affixed to the sliding chassis 102 and the fixed portion 101 respectively. The fixed cam member 103 is provided with cam surfaces 105 and the movable cam 104 is provided a cam surface 106. A cam pin 107 pivotably mounting a movable arm, or tensioning arm, 109 is provided, movable along the cam surfaces 105 and 106. The cam pin 107 is associated with a coil spring 108 which urges the tensioning arm 109. The tensioning arm 109 is movable along the cam surface 105 of the fixed cam to the cam surface 106 of the movable cam 104. The tensioning arm 109 is moved according to rotation of the movable cam 104 and comprise a portion of a tension regulator for a VTR, for example.
According to the above, a tension regulator arrangement typically comprises a fixed chassis, with a fixed cam and a movable cam installed thereon, and a sliding chassis with a tensioning arm installed thereon for movement with the sliding chassis.
As applied to operation in a VTR, the sliding chassis is associated with a cassette holder for accepting a cassette tape cartridge therein. According to pushing force applied to the cassette holder, the sliding chassis slides, causing the cam pin to move along the cam surface of the fixed cam. This in turn causes the tensioning arm to rotate and draw a portion of tape from the tape cassette.
Further, after the movement of the cam pin along the surface of the fixed cam reaches the cam surface of the movable cam the sliding of the slidable chassis is stopped. Tape angle guides, associated with the supply and take-up reels of the cassette disposed on the sliding chassis, are movable to wind the tape around an outer surface of a rotatable head drum at a predetermined winding angle. Thereafter the movable cam rotates to cause the tensioning arm to move to effect adjustment of tape tensioning.
In such conventional cam arrangements, the movement of the cam pin is determined along the cam surface of the fixed cam to the cam surface of the movable cam, and the tensioning effected by the tensioning arm is dependent upon motion transmitted by the rotating movement of the movable cam. However, due to the mechanical characteristics of the arrangement, slippage may occur between the movable cam and the tensioning arm which may cause misoperation, especially at a point where a cam pin associated with the tensioning arm moves from the cam surface of the movable cam to the cam surface of the fixed cam. This can cause the cam pin to become jammed as seen in FIG. 8. This is especially true of portable cassette units, for example, which may be subject to accidental jarring or shocks during use.
Therefore, it has been required to provide a tape tensioner which may avoid such a condition to compensate for such slippage and provide reliable tape loading and tensioning.